1. Technical Field
The present invention relates to imaging systems and, more particularly, to imaging systems in which a changing direction-of-view of the images is coupled to a changing direction-of-view of the head of the viewer.
2. Description of Related Art
Certain imaging systems provide the user with a light stimulus in the form of images (or for forming images) and provide other sensory stimuli as well to immerse the user in an artificial world that seems real. In active systems, movements of the user are sensed and used as inputs to a “virtual reality” engine that selects and provides the images and other sensory stimuli according to the sensed movements. In particular, the position and attitude of the head of the viewer can be monitored in three-dimensional space by several different methods. By “position” of the head is meant the translations in a three-dimensional space of the monitored head or of an arbitrary point associated therewith. By “attitude” of the head is meant the direction or direction-of-view of the monitored head or the arbitrary point. Its meaning is analogous to “attitude” in an aircraft, i.e., pitch, roll and yaw. Among these monitoring methods are: (a) the method and apparatus shown in U.S. Pat. No. 5,615,132 for determining position and orientation of a moveable object using accelerometers, (b) the image display method and apparatus with means for yoking viewpoint orienting muscles of a user shown in U.S. Pat. No. 5,436,638, and (c) optical methods such as shown in U.S. Pat. No. 5,835,224 or U.S. Pat. No. 5,729,475. Sensed signals indicative of the position and attitude of the head are input to the reality engine which then generates images having a positional point-of-view as well as a direction-of-view that changes in correspondence with changes in the position and direction-of-view of the head of the user. In passive systems, such as shown in U.S. Pat. No. 5,734,421, the head of a passive user is guided in plural degrees of freedom by an actuator to view an artificial world from various positions and directions-of-view. However, these various approaches suffer from a twofold problem. First, the known active and passive systems require the user to address the imaging system with an erect standing or seated posture that can be physically wearying over extended periods. Second, in the context of active applications, such as entertainment, they require the user to exert a degree of activism that can be overly demanding and even disconcerting. Such requirements are the antithesis of the relaxed entertainment experience preferred by most users.